Spinal cord injuries and stroke afflict a significant component of our population (both the young and the aging). The lack of effective therapeutic solutions to these problems results in the need for lifetime care and expensive assistive technologies for these individuals. The decrease in the quality of life of these patients, the costs of their chronic care, and the reduction in their productivity present strong motivations to develop new therapeutic approaches to this problem. The goal of restoring motor function to individuals with spinal cord injuries or stroke victims has been hampered by the lack of an appropriate interface to the peripheral nervous system. The development of a minimal error control system for restoration of motor function will require acquisition of sensory information from a large number of cutaneous, muscle and joint receptors, and the capability of independent excitation of a large number of muscle groups. Existing neural interfaces cannot provide such multichannel independent access to sensory and motor nerve fibers. We have developed a new neural interface, the Utah Slant Array (or USA) that will provide unprecedented access to large number of sensory and motor neurons. The array has been designed to be implanted in peripheral nerves, and will provide up to 100 channels of neural communication. We will evaluate the recording and stimulating capabilities of the USA in acute experiments in feline sciatic nerve. We will develop a chronic USA implant system based upon what we have learned in our acute experiments, and evaluate its chronic recording and stimulating stability in an ambulating cat. We will demonstrate that sensory information recorded with the USA can be used to control the motor stimulation of efferent fibers to achieve a reliable control of a cat's ankle and foot movements when walking on a treadmill. Our overall goal is to acquire sufficient information about the USA and how it can be chronically applied so that human application would be feasible and ethically acceptable in a future granting period.